Recently, a hybrid power supply system in which a storage cell is connected in parallel with a fuel cell as a power generating device such that both the fuel cell and the storage cell supply electric power to a load has been developed. It is considered that such a power supply system compensates for the lack of electric power generated by the fuel cell for power consumption in the load due to response characteristics (or response delay) of the electric power by output power from the storage cell (Patent Literature 1).